I know this isn't super traditional, but I'm not intending on serving it to Charlie Palmer, or anyone from France.  The tuna, also known as prickly pear, from cacti, has very little pectin in it.  This is why, third party pectin is required to make a jelly.  Since tuna jelly was made long before liquid pectin was available in stores, I attempted to stew the rinds to get more pectin into the mixture.  This created more of a thick syrup.

I asked Rick Bayless about the matter, and he replied, "To my knowledge you have to use pectin. Doubt there's enough pectin in rind. Could use apple cores."  I think this is a good workaround for the jelly.  Also, I've theorized that the term jelly meant something different 100+ years ago compared to today.  So when I say tuna jelly, be open-minded, and don't think about fish.